Well, I'll show you how I got my date.
Diamond and Pearl came out on September 28, 2006 in JP and came out on April 22, 2007 for the US
Platinum was 13 days earlier for Japan and a Month earlier for the US.
When HG/SS went a day earlier for Japan it was a week earlier for the US.
If B/W are now a week later, wouldn't they be somewhere along the lines of two weeks earlier for the US?
Also, HG/SS came out March 14 this year, which is no where near the 20's.
Enter the Shattered Realm - At your own discretion.
Shoutout to the year I only used liking FS/N to have an excuse to make signatures